and 316 m on sand (3/11) and sand-silt (8/11) sedi- 

 ments. 



Unciola sp. B 



Single specimens of an undescribed species of Unciola 

 were collected at four stations between New Jersey and 

 Caf)e Hatteras on the continental slope (Fig. 11). These 

 stations were located between 400 and 505 m on silty 

 sand sediments. 



Family EUSIRIDAE 



Pontogeneia inermis (Kri^yer) 1938 



Geographic Distribution. This species is widely dis- 

 tributed in the arctic boreal regions, and it has previous- 

 ly been recorded as far south as Long Island off the east 

 coast of North America (Bousfield 1973). We collected 

 P inermis at 15 stations extending from Cape Cod to 

 Virginia (Fig. 12). The three records between Long 

 Island and Virginia constitute a southern range exten- 

 sion for this species. Pontogeneia inermis was moderate- 

 ly abundant with a mean density of 80/m^ ranging from 

 2/m^ to 70O/m2. The three southern stations had low 

 densities (2-8/m^). 



Bathymetric Distribution. Pontogeneia inermis is 

 reported to occur between the low intertidal and depths 

 over 10 m. We collected this species in samples from be- 

 tween 18 and 73 m with the highest densities (380/m^), 

 occurring between 40 and 49 m (Table 23). It is worth 

 noting that our records of this species are from signifi- 

 cantly greater depths than the bathymetric range sug- 

 gested by Bousfield (1973). The most likely explanation 

 is that P. inermis submerges in the southern portion of 

 its range. 



Table 23.— Bathymetric distribution of Pontogeneia 

 inermis in samples from Middle Atlantic Bight. 



Table 24.— Sediment associations of Pontogeneia 

 inermis in samples from .Middle .Atlantic Bight. 



Sediment Relationship. Bousfield (1973) reported that 

 this species is pelagic and epibenthic, and that it clings 

 to submerged plants and algae. In our collections, P. in- 

 ermis occurred most frequently on sand bottoms (8/17), 

 but its density was highest (240/m2) on gravelly sedi- 

 ments (Table 24). It seems likely that in the deeper 

 waters from which we collected this species it clings to 

 hydroids, bryozoans, and other plantlike invertebrates, 

 since there are no macroalgae at these depths. 



Rhachotropia inflata 

 (G. O. Sars) 1882 



This species has previously been recorded in the 

 North Atlantic and northeast Pacific and in the west- 

 em Atlantic; it occurs from the Arctic to the Gulf of St. 

 Lawrence (Barnard 1971; Bousfield 1973). A single 

 specimen was found in our collections from a station 

 located offshore of Chesapeake Bay at a depth of 104 m 

 on a sand-shell bottom (Fig. 12). Although this record 

 extends the range of this species, R. inflata is clearly 

 rare south of Cape Cod. 



Family GAMMARIDAE 



Ca8co bigelowi (Blake) 1929 



Geographic Distribution. According to Bousfield 

 (1973), this species has been collected from the Gulf of 

 St. Lawrence to New Jersey off the east coast of North 

 America. In our collections from the Middle Atlantic 

 Bight, C. bigelowi occurred in 41 samples from 32 sta- 

 tions located between Cape Cod and Maryland (Fig. 13). 

 It was found in low densities at all stations with a mean 

 ot 'iO/m-, ranging between 2/m- and 60/m-. This species 

 is much more common in the northern part of our study 

 area, but the single deep water (400 m) record off Mary- 

 land does constitute a slight southerly extension of its 

 range. 



Bathymetric Distribution. Bousfield (1973) gave the 

 depth range of this species as low intertidal to >50 m. 

 We collected C. bigelowi between 33 and 400 m with the 

 bulk of our collections (37/41) occurring between 40 and 

 100 m (Table 25). The discrepancy between the depth 



Table 25.— Bathymetric distribution of Casco bige- 

 lowi in samples from Middle Atlantic Bight. 



22 



